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“Plug & Produce” Functions for a Robotic Assembly Cell

Holonic Manufacturing Systems offer a novel paradigm to address some critical problems faced by manufacturing as it comes to grips with the 21st Century market. This is particularly so when there is demand for mass customisation. Holons are autonomous cooperating entities – essentially, agents.

Traditional manufacturing control systems are hierarchical and are geared to mass production of low-variety goods. Often a schedule of the manufacturing operations on a given day is developed well in advance. As the schedule is executed, unexpected events, typical of many production, warehousing and supply chain environments, tend to invalidate the schedule and change how operations are managed. These events include machine failures. Holonic Manufacturing Systems offer a solution to this problem, providing a dynamically reconfigurable architecture that can respond to changes in manufacturing requirements.

There are many practical problems in implementing holonic manufacturing systems. One well known problem is that of calibrating a robot once it has been installed at a new station in response to a need to reconfigure the system. This is typically performed manually, i.e. the human operator has to line up the robot's gripper with the station's guide marks. Arai, Maeda and colleagues report on a new semi-automated approach to reconfigurability (in press: "Plug & Produce Functions for an Easily Reconfigurable Robotic Assembly Cell").

The robot installation procedure is as follows:

The new robot announces its approximate position to the other entities and requests that neighbouring devices halt their assembly operations temporarily, in the interests of collision avoidance.

The new robot waits for its neighbours to confirm that they have suspended operations.

The robot executes an automated calibration procedure.

The calibration graph of the system is updated.

Workspace information is updated according to the calibration graph and movable areas of the robots.

The adjacency graph is updated to reflect changes in workspace information.

Now, the robot installation is completed. The new robot informs the neighbouring devices that they can now resume their suspended assembly operations.

Experiments confirm that the system is able to automatically recalibrate the added robot so that it can take part in assembly operations.

The experimental system is part of their ongoing work with JACK® and holonic manufacturing.